The original 273 gaskets were about .026 compressed and not perfectly round but it fit the 273 chambers well. The A measurement is 3.815 and the B measurement is 3.975. If the OP wants the optimum head gasket he should contact Cometic. Really not necessary though with a used engine. I used the MP composite ones (like the Mr. Gasket 1121G's) They worked fine.
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